Production of monochloroacetyl chloride and monochloroacetic acid by hydration of trichloroethylene

ABSTRACT

Continuous process for the production of monochloroacetyl chloride accompanied, if the need should arise, by monochloroacetic acid, from trichloroethylene and/or 1,1,1,2-tetrachloroethane by reaction for hydration of trichloroethylene and/or 1,1,1,2-tetrachloroethane under pressure of hydrogen chloride in liquid phase, in the presence of ferric chloride in partial suspension.

The present invention concerns a process for the production ofmonochloroacetyl chloride accompanied if need be by monochloroaceticacid, by hydration of trichloroethylene and/or1,1,1,2-tetrachloroethane, in the presence of an iron chloride catalyst.

It is known for monochloroacetic acid to be prepared in accordance withU.S. Pat. No. 1,304,108 by the hydration reaction of trichloroethyleneat a temperature of from 150° to 200° C., in the presence of sulphuricacid in a concentration of at least 95% or in the presence of oleum, asthe hydration agent.

The patentees take as their basis the performance of hypotheticalreactions, in order to explain the formation of monochloroacetic acid,such reactions being as follows:

    SO.sub.4 H.sub.2 +CCl.sub.2 ═CHCl→SO.sub.2 (OH)--O--CCl.sub.2 --CH.sub.2 Cl

    SO.sub.2 (OH)--O--CCl.sub.2 --CH.sub.2 Cl+H.sub.2 O→SO.sub.4 H.sub.2 +CCl.sub.2 (OH)--CH.sub.2 Cl

    CCl.sub.2 (OH)--CH.sub.2 Cl→CH.sub.2 Cl--COCl+HCl

    CH.sub.2 Cl--COCl+H.sub.2 O→CH.sub.2 Cl--COOH+HCl

which, taken overall, makes it seem as if water alone produces theconversion effect:

    CCl.sub.2 ═CHCl+2H.sub.2 O→CH.sub.2 Cl--COOH+2HCl

However, the intermediate formation of monochloroacetyl chloride has notbeen demonstrated or displayed, as is clearly apparent from French Pat.No. 516,367 which specifies production of monochloroacetic acidexclusively, by reacting water and trichloroethylene in the presence of90% sulphuric acid at a temperature of 190° C.

Swiss Pat. No. 86,192 specifically describes the production ofmonochloroacetyl chloride from trichloroethylene, also by heating atabout 110° C. with sulphuric acid but in the anhydrous state (100%).This process cannot therefore involve a trichloroethylene hydrationreaction.

More recently, U.S. Pat. No. 3,742,047 described a process for producingmonochloroacetyl chloride by reacting a mixture of trichloroethylene andmonochloroacetic acid with a derivative of sulphonic acid or sulphuricacid at a temperature of from 75° to 125° C. The acid used in thisreaction is essentially free from water, such as 100% sulphuric acid ortoluenesulphonic, methanesulphonic, ethanesulphonic and chlorosulphonicacids. In the case of 100% sulphuric acid, the reaction may be writtenas follows:

    CHCl═CCl.sub.2 +Cl--CH.sub.2 --COOH+H.sub.2 SO.sub.4 →2ClCH.sub.2 --COCl+H.sub.2 SO.sub.4

however, this process consumes monochloroacetic acid, while in itself itis a useful starting product for many synthesis operations, for examplethat of compounds which enjoy herbicidal properties or parasiticidalproperties, containing the chloroacetyl group. In addition, performanceof the reaction requires strict monitoring of the temperature which mustnot exceed 125° C. as, above that temperature, polymerization,sulphonation and dehydration (anhydrides) by-products are formed.

According to French Pat. No. 2,070,428, this last reaction can beperformed under hydrogen chloride pressure, but using ferric chloride asthe catalyst instead of sulphuric or sulphonic acid. However, like theabove-mentioned process, this process also consumes monochloroaceticacid. In addition, for continuous operation of the process, it isnecessary to introduce under pressure monochloroacetic acid in themolten state, and the anhydrous catalyst in solid form, whiletrichloroethylene is in liquid phase. These operations give rise totechnical problems which are difficult to overcome.

The process disclosed in French Pat. No. 2,070,427, which differs fromthat of the preceding French patent only by the starting reagent whichis 1,1,1,2-tetrachloroethane, instead of trichloroethylene, suffers fromthe same technical difficulties which impede easy performance of theprocess on an industrial scale.

The aim of the present invention is to overcome the abovementioneddisadvantages by using a simple process for the continuous production ofmonochloroacetyl chloride, accompanied, if necessary, bymonochloroacetic acid, by the direct action of water ontrichloroethylene, in accordance with the following reaction:

    CHCl═CCl.sub.2 +H.sub.2 O→ClCH.sub.2 --COCl+HCl

According to the invention, water is reacted with trichloroethyleneand/or 1,1,1,2-tetrachloroethane, said hydration reaction being effectedin liquid phase in the presence of ferric chloride, partially insuspension, and under hydrogen chloride pressure, at a temperature offrom 80° to 180° C.

The hydrogen chloride pressure for carrying out the process of theinvention is from 5 to 80 bars absolute pressure, more advantageouslyfrom 15 to 60 bars absolute pressure, and preferably from 20 to 40 barsabsolute pressure.

It has been found that reaction speed reaches a maximum value at aspecific temperature for a given pressure within the described range.This makes it possible to define a preferred temperature range whichembraces that specific temperature for the selected operating pressure.For example, when operation is at a pressure of 30 bars absolute, it isobserved that, at temperatures below 100° C. and at temperatures above180° C., reaction is virtually negligible, and the speed of reactionbegins to decrease from about 160° C., so that the preferred reactiontemperature range is from 140° to 170° C.

According to the invention, the molar ratio between the feed reagentstrichloroethylene and/or 1,1,1,2-tetrachloroethane and water isgenerally at least 0.6. It is found that the amount of monochloroaceticacid which accompanies the monochloroacetyl chloride increases as themolar ratio between the feed trichloroethylene and/or1,1,1,2-tetrachloroethane and water approaches a value of 0.6. Incontrast, when this molar ratio assumes values above 2, the amounts ofundesirable secondary products such as pentachloroethane andperchloroethylene, resulting from the additive chlorination oftrichloroethylene by FeCl₃ and the attendant reduction of a part ofFeCl₃ to FeCl₂, and pentachlorobutadiene resulting from the dimerizationof trichloroethylene become evident and even substantial, so that it isvery possible to operate at molar ratios of from 2.5 to 3 for example,if such secondary products are desired.

In the event that it is desired to produce monochloroacetyl chloridewith a very good degree of selectivity, it is desirable to use molarratios of feed trichloroethylene and/or 1,1,1,2-tetrachloroethane towater of from 1.2 to 1.8.

When it is desired simultaneously to produce substantial amounts ofmonochloroacetyl chloride and monochloroacetic acid, the molar ratiobetween the feed trichloroethylene and/or 1,1,1,2-tetrachloroethane andwater is selected at a value of from 0.6 to 1.2.

The amount of ferric chloride which is introduced into the reactionmedium is from 0.1 to 15% by weight of the reaction medium except forthe hydrogen chloride, both in gaseous form and that which is dissolvedtherein. Below a value of 0.1% by weight of FeCl₃, the reaction speed isexcessively slow, whereas above 15% by weight, the separation andsubsequent recovery of the catalyst in the reaction medium becomecomplicated. When ferrous chloride is formed, in consequence of theundesired reactions set out above, the catalyst may be separated fromthe reaction medium by any known means and the ferrous chloride may bere-oxidized to FeCl₃ by gaseous chlorine or an agent capable ofliberating the active chlorine such as chlorine water, Javel water, orchlorine dioxide or, generally, by any HCl oxidizing agent. The catalystwhich is regenerated in this way can then be recycled to the reactionmedium.

In accordance with a particularly advantageous embodiment of the processof the invention, the ferric chloride is introduced into the reactionmedium in the form an an aqueous solution.

In a method of recovery of the catalyst, within the scope of the processof the invention, the effluent from the reaction zone is subjected to afractionation to separate the unreacted chlorinated hydrocarbons and themonochloroacetyl chloride, from the mixture containing the ferrous andferric chlorides. This mixture is treated with water and re-oxidized,for example, by chlorine, and the resulting ferric solution is thenrecycled to the reaction zone.

The residence time of the reactants in the reaction zone, calculated onthe input flow rates, is generally from 1 to 8 hours and preferably from2 to 6 hours.

According to the invention, the starting trichloroethylene may originatefrom 1,1,1,2-tetrachloroethane which, under the conditions of thehydration reaction of the invention, undergoes at least partialdehydrochlorination, in situ, to trichloroethylene, thus establishing anequilibrium, which depends on the temperature and pressure used, between1,1,1,2-tetrachloroethane and trichloroethylene. So that it is possiblefor the starting product used according to the invention, to betrichloroethylene and/or 1,1,1,2-tetrachloroethane, which is expressedby the molar ratio between the reagents trichloroethylene and/or1,1,1,2-tetrachloroethane and water.

Thus, within the scope of a continuous process,1,1,1,2-tetrachloroethane, in the same way as monochloroacetic acid, isa useful by-product which may be recycled with the trichloroethylene ofthe feed. As for its part, the monochloroacetic acid which is possiblyformed, may, if desired, advantageously be recycled in mixture with theferric chloride, particularly when the latter is used in the form of anaqueous solution. In such instance, the amount of ferric chloride isgreater than 20% by weight with respect to the quantity ofmonochloroacetic acid present in the reaction medium, and may exceed upto ten times the weight of that acid which is present.

The following examples are given by way of illustration and not by wayof limitation of the present invention.

In these examples, the conversion rate of trichloroethylene and/or1,1,1,2-tetrachloroethane used, according to circumstances, as thestarting substance, is defined by the ratio: ##EQU1## with the numeratorequal to the difference between the number of moles of (CCl₂ ═CHCl+CCl₃CH₂ Cl) fed to the reactor, and the number of moles of (CCl₂ ═CHCl+CCl₃CH₂ Cl) exiting from the reactor.

The selectivity in respect of ClCH₂ --COCl is defined by the ratio:##EQU2##

The selectivity in respect of ClCH₂ --COOH is defined by the followingratio:

EXAMPLE 1

1264 kg/h (9.61 kmoles) of trichloroethylene and 181 kg/h of an aqueoussolution of FeCl₃ containing 40.3% of FeCl₃ (0.45 kmole of FeCl₃ and 6kmoles of H₂ O) are continuously introduced into a glass-lined steelreaction vessel which is agitated and provided with pressure and levelcontrol means.

The molar ratio between the trichloroethylene and water is 1.6 and theamount of FeCl₃ represents 5.8% by weight of the reaction medium exceptfor HCl (both in gaseous form and that which is dissolved therein).

The pressure in the reactor is maintained at 30 bars absolute pressureand the temperature is fixed at 150° C. The residence time of thereagents is 4 hours. From the reactor, there is continuously drawn 1257kg/h of liquid apart from dissolved HCl containing:

656.5 kg of monochloroacetyl chloride

9.5 kg of monochloroacetic acid

366 kg of trichloroethylene

141 kg of 1,1,1,2-tetrachloroethane

16 kg of chlorinated heavy substances (boiling point >150° C.)

49 kg of FeCl₃

19 kg of FeCl₂

A total of 5.16 kmoles/h of HCl is recovered, corresponding to the HCldrawn off continuously in the gaseous phase and to the dissolved HClevolved by subsequent pressure release of the liquid effluent.

In order to recover the catalyst, this effluent is fractionated toseparate the monochloroacetyl chloride and the unreacted chlorinatedhydrocarbons, from the mixture containing the ferrous and ferricchlorides. This mixture is treated with water and re-oxidized bychlorine to give a ferric solution before being recycled to the reactor.

The conversion rate, the degrees of selectivity in respect of ClCH₂--COCl and ClCH₂ --COOH as defined above are respectively 62.3%, 97.0%and 1.7%.

EXAMPLE 2

Following the same stages of the process and under the same temperatureand hydrogen chloride pressure conditions as set out in Example 1, 1151kg/h (8.75 kmoles) of trichloroethylene and 266.5 kg/h of an aqueoussolution of FeCl₃ containing 27.3% by weight of FeCl₃ (10.75 kmoles ofH₂ O and 0.45 kmoles/m³ of FeCl₃) is continuously introduced into thereactor.

The trichloroethylene/water molar ratio is 0.81. The amount of FeCl³represents 7.1% by weight of the reaction medium except for HCl (boththat dissolved and that in gaseous form).

The intake flow rate of the reagents is 1 m³ /h. The residence time ofthe reagents in the reactor is 4 hours. 1032 kg/h of the followingreaction product, apart from dissolved HCl, is drawn off from thereactor:

430.5 kg of monochloroacetyl chloride

328 kg of monochloroacetic acid

167 kg of trichloroethylene

32 kg of 1,1,1,2-tetrachloroethane

2 kg of chlorinated heavy products (boiling point >150° C.).

70 kg of FeCl₃

2.6 kg of FeCl₂

10.56 kmoles/h of HCl recovered.

The conversion rate, the degrees of selectivity of CH₂ Cl--COCl and CH₂Cl--COOH as defined above are respectively 83.3%, 52.3% and 47.6%.

EXAMPLE 3

Following the same steps of the process and under the same temperature,residence time and hydrogen chloride pressure conditions as set out inExample 1, the following are continuously introduced into the reactor:

1249.5 kg/h (9.5 kmoles) of trichloroethylene

190.5 kg/h (7.6 kmoles H₂ O and 0.33 kmoles FeCl₃) of aqueous solutionof FeCl₃ containing 28.1% by weight of FeCl₃.

The trichloroethylene/water molar ratio is 1.25. The amount of FeCl₃represents 4.5% by weight of the reaction mixture except for thehydrogen chloride which is dissolved therein, and also that which is inthe gaseous state.

The intake flow rate of the reactants is 1 m³ /h.

1188.5 kg/h of the following reaction product, apart from dissolved HCl,is drawn from the reactor:

447 kg of monochloroacetyl chloride

172 kg of monochloroacetic acid

393 kg of trichloroethylene

119 kg of 1,1,1,2-tetrachloroethane

6 kg of chlorinated heavy products (boiling point >150° C.)

45.5 kg of FeCl₃

6 kg of FeCl₂

6.89 kmoles/h of HCl recovered.

The conversion rate, the degrees of selectivity in respect of CH₂Cl--COCl and CH₂ Cl--COOH as defined above are respectively 61.1%, 68.3%and 31.4%.

EXAMPLE 4

Carrying out the same steps of the process and under the sametemperature and HCl pressure conditions as set out in Example 1, thefollowing are continuously introduced into the reactor:

1663.5 kg/h (12.65 kmoles) of trichloroethylene

260.5 kg/h (9.05 kmoles H₂ O and 0.6 kmole FeCl₃) of aqueous solutioncontaining 37.4% by weight of FeCl₃.

The trichloroethylene/water molar ratio is 1.4. The intake flow rate ofthe reagents is 1.33 m³ /h. The residence time of the reagents in thereactor is 3 hours. The amount of FeCl₃ represents 5.9% by weight withrespect to the reaction medium apart from HCl (both that in the gaseousstate and that in the dissolved state).

1649 kg/h of reaction product apart from dissolved HCl is then drawnfrom the reactor:

545 kg of monochloroacetyl chloride

200 kg of monochloroacetic acid

539 kg of trichloroethylene

254 kg of 1,1,1,2-tetrachloroethane

24 kg of chlorinated heavy products (boiling point >150° C.)

57 kg of FeCl₃

30 kg of FeCl₂

7.54 kmoles/h of HCl recovered.

The conversion rate, the degrees of selectivity in respect of CH₂Cl--COCl and CH₂ Cl--COOH as defined above are respectively 55.7%, 68.5%and 30.1%.

EXAMPLE 5

Under the same temperature and HCl pressure conditions and performingthe same steps in the process as set out in Example 1, the following arecontinuously introduced into the reactor:

1097 kg of trichloroethylene

196 kg/h of recycled 1,1,1,2-tetrachloroethane resulting from theeffluent of the reactor

110 kg/h of water

90 kg/h of recycled monochloroacetic acid also resulting from theeffluent of the reactor

66 kg/h of FeCl₃ of which 95% comes from recycling of the catalystrecovered from the effluent of the reactor

The molar ratio between (CHCl═CCl₂ +CCl₃ --CH₂ Cl) and H₂ O is 1.56. Theintake flow rate into the reactor of the components of the reactionmixture is about 1 m³ /h, and the residence time of the components inthe reactor is four hours. The amount of FeCl₃ represents 4.9% by weightof the reaction medium HCl excepted (both that in the dissolved stateand that in the gaseous state).

1336 kg/h of the following reaction mixture, except for dissolved HCl,is drawn from the reactor:

690.5 kg of monochloroacetyl chloride

90 kg of monochloroacetic acid

284 kg of trichloroethylene

196 kg of 1,1,1,2-tetrachloroethane

14.5 kg of chlorinated heavy products (boiling point >150° C.)

45 kg of FeCl₃

16 kg of FeCl₂

6.11 kmoles/h of HCl recovered

The conversion rate of the feed trichloroethylene and1,1,1,2-tetrachloroethane, and the selectivity in respect of ClCH₂--COCl as defined above are respectively 65% and 98.9%.

EXAMPLE 6

Under the same temperature and HCl pressure conditions and carrying outthe same operations as set out in Example 1, the following arecontinuously introduced into the reactor;

2125 kg/h of 1,1,1,2-tetrachloroethane

260.5 kg/h (9.05 kmoles H₂ O and 0.6 kmole FeCl₃) of aqueous solutioncontaining 37.4% by weight of FeCl₃.

The 1,1,1,2-tetrachloroethane/water molar ratio is 1.4 and the intakeflow rate of the reagents is 1.49 m³ /h.

The residence time of the reagents in the reactor is 2.7 hours. Theamount of FeCl₃ represents 6% by weight with respect to the reactionmedium except for HCl (both that in the dissolved states and that in thegaseous state).

1632.5 kg/h of the following reaction product, except for dissolved HCl,is then drawn from the reactor:

864.5 kg of monochloroacetyl chloride

65 kg of monochloroacetic acid

393 kg of trichloroethylene

201.5 kg of 1,1,1,2-tetrachloroethane

18 kg of chlorinated heavy products (boiling point >150° C.)

25.5 kg of FeCl₂

65 kg of FeCl₃

20.6 kmoles/h of HCl recovered

The conversion rate of 1,1,1,2-tetrachloroethane and the degrees ofselectivity in respect of CH₂ Cl--COCl and CH₂ Cl--COOH are respectively66.9%, 90.4% and 8.2%.

We claim:
 1. A continuous process for the production of monochloroacetylchloride, which may be accompanied by monochloroacetic acid, fromtrichloroethylene and/or 1,1,1,2-tetrachloroethane, comprising hydratingtrichloroethylene and/or 1,1,1,2-tetrachloroethane under pressure ofhydrogen chloride in liquid phase in the presence of ferric chloridepartially in suspension, in which the hydrogen chloride pressure iswithin the range of 5-80 bars absolute.
 2. A process as claimed in claim1 characterized in that hydration is effected at a temperature of from80° to 180° C.
 3. A process as claimed in claim 1 characterized in thathydration is effected at a temperature of from 140° to 170° C.
 4. Aprocess as claimed in claim 1 in which the ferric chloride is introducedinto the reaction medium in the form of an aqueous solution.
 5. Aprocess as claimed in claim 1 in which the trichloroethylene and/or1,1,1,2-tetrachloroethane and water are introduced into the reactionzone in a molar ratio greater than 0.6.
 6. A process as claimed in claim1 in which the trichloroethylene and/or 1,1,1,2-tetrachloroethane andwater are in a molar ratio of from 1.2 to 1.8.
 7. A process as claimedin claim 1 in which the trichloroethylene for the feed originates atleast partially from the in situ dehydrochlorination of1,1,1,2-tetrachloroethane.
 8. A process as claimed in claim 1 in whichthe trichloroethylene for the feed originates from the in situdehydrochlorination of 1,1,1,2-tetrachloroethane.
 9. A process asclaimed in claim 1 in which any monochloroacetic acid which is formed isrecycled to the reaction medium.
 10. A process as claimed in claim 1 inwhich the amount of FeCl₃ is from 0.1 to 15% by weight of the whole ofthe reaction medium, except for the hydrogen chloride both in thegaseous state and that which is dissolved therein.
 11. A process asclaimed in claim 1 in which monochloroacetic acid is formed and isrecycled in mixture with the ferric chloride solution.
 12. A process asclaimed in claim 11 in which the amount of ferric chloride is higherthan 20% by weight with respect to the amount of monochloroacetic acidpresent in the reaction medium.
 13. A process as claimed in claim 1 inwhich the hydrogen chloride pressure is from 5 to 80 bars absolute. 14.A process as claimed in claim 1 in which the hydrogen chloride pressureis from 20 to 40 bars absolute.
 15. A process as claimed in claim 1 inwhich, in the case where the ferric chloride of the reaction mediumgives ferrous chloride as a consequence of secondary reactions, theferrous chloride is re-oxidized by active chlorine to FeCl₃.
 16. Aprocess as claimed in claim 12 comprising fractionating the reactionmedium effluent to separate the unreacted chlorinated hydrocarbons andmonochloroacetyl chloride from the mixture containing the ferrous andferric chlorides before reoxidation of the ferrous chloride.